Handlebar extension



FIG. 1 is a side elevational view of a handlebar extension showing my new design;

FIG. 2 is an end elevational view thereof;

FIG. 3 is an elevational view from the opposite end from that shown in FIG. 2;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a perspective view thereof, the handlebar and grip shown in broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a handlebar extension, as shown and described. 